too many idle sessions

Hi fellows, in our database we have a lot of idle session, these sessions are impacting in memory usage and in available database connections. These idle sessions are generated by our web applications that use IIS generating pool session.

 

To work around with this issue, we are monitoring idle sessions that have 4 hours to kill these sessions. Before adopt this procedure, we have configure the parameter idle of users profile, but give us problems with our web application because the idle sessions were not killed.

 

Any suggestion how can we improve  to reduce substantially the idle session without executing manually our kill sessions procedure?, we probe also executing this procedure with a job but sometimes the job don’t execute satisfactorily because find a session mark to kill or session is not available